Page 2 of 3 FirstFirst 123 LastLast
Results 11 to 20 of 25

Thread: Suggest a Microcontroller for Delta Robot Project

  1. Re: Suggest a Microcontroller for Delta Robot Project

    Quote Originally Posted by tician View Post
    8.2mm steps in position control, at best, is good? Granted, even the AX-12 will have only ~2.3mm steps with a 45cm arm. What do you think any hobby servos will actually be able to accomplish with control resolution that poor and usable torque levels that low (16[kg-cm]*(1/5) / 45[cm]=0.071[kg])?
    I know that 8.2mm step in position control is not good. My project advisor allows me with step size of 10mm. So that's allowable.

    Most important thing, Dynamixel servos are not available in Pakistan. I have contacted to hobbyKing guy for Dynamixel Intelligent Robot Servo but shipping will cost too much from USA store to Pakistan and also i do not have that time to wait for dynamixel from HobbyKing.

    I have found some dynamixel on ebay but the vendor either does not ship to Pakistan or there is cost/time related issues.

  2. Re: Suggest a Microcontroller for Delta Robot Project

    There are delta robots over Internet in which hobby servos not more 10Kg-cm are used but they work like a charm and using Arduino with time control technique (Not a solution i think) for driving three servos simultaneously with different position values.

    So for a 10Kg-cm servo and 30cm link, end effector torque is 0.06kg. I did not understand that point.

    I am new to robotics as I have told earlier. If I am wrong at something, please correct me.

  3. #13
    Join Date
    Jan 2008
    Location
    Norway, Stavanger
    Posts
    790
    Images
    276
    Rep Power
    78

    Re: Suggest a Microcontroller for Delta Robot Project

    Hi,
    Do you have any sketches of your delta robot? I assume you are not going to have a 45cm arm on the servo, but a 45cm long link? Similar to this?
    Kåre Halvorsen aka Zenta
    ---------------------------------
    Zenta's YouTube channel
    Zenta's Blog
    Zenta's Instagram

  4. Re: Suggest a Microcontroller for Delta Robot Project

    Quote Originally Posted by Zenta View Post
    Hi,
    Do you have any sketches of your delta robot? I assume you are not going to have a 45cm arm on the servo, but a 45cm long link? Similar to this?
    Yeah you are right, My group fellow has made a model of delta robot on Solid Edge, and i have asked him about link length, its not more than 32cm. (Correction Here)

    Also the link is same as you have provided in the web-link. Each link has two parts 1- Upper Arm about 5-6cm and 2- Lower arm About 25-26cm so total link length of almost 32cm.

  5. Re: Suggest a Microcontroller for Delta Robot Project

    Quote Originally Posted by Zenta View Post
    Do you have any sketches of your delta robot?
    Here is screenshot of BOM File. The Design and dimension are not final yet and can be changed if required.

    Click image for larger version. 

Name:	Delta BOM.PNG 
Views:	361 
Size:	135.6 KB 
ID:	5732
    Last edited by ahmadbilal3000; 12-07-2014 at 12:50 PM.

  6. #16
    Join Date
    Sep 2010
    Location
    ಠ_ಠ
    Posts
    2,283
    Images
    27
    Rep Power
    275

    Re: Suggest a Microcontroller for Delta Robot Project

    The point was that those servo and link selections (16kg-cm; 45cm) would give you only ~70gf continuous force, which is barely enough to push some non-levered snap-action buttons. I would not be surprised if the servos were incapable of actually supporting the weight of those links/arms for any significant length of time. The shorter 5~6cm control arms give you ~0.6kgf to push and pull on the pin connections to the lower links, which is more likely to be able to support the weight of the links and platform but not sure how much else it can carry/move. Have you actually done any sort of estimation of the torque required to support the load you are intending to control? This is first-year MechE statics stuff: given a space-frame and loading (system design requirements), what is the torque experienced/required at the supports (required component minimum specifications)?

    Will you stop with the 'arduino not a solution' crap? Even a long-time obsolete 86HC11 is fully capable of controlling three cheap hobby servos simultaneously. Have you not seen some of the very awesome 3/4-DOF per leg, 4/6-legged crawlers controlled by the SSC-32 (ATmega328)? They require a lot more PWM servos to be accurately controlled in parallel than your delta, yet no issues whatsoever smoothly walking and dancing.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  7. #17
    Join Date
    Jan 2008
    Location
    Norway, Stavanger
    Posts
    790
    Images
    276
    Rep Power
    78

    Re: Suggest a Microcontroller for Delta Robot Project

    Thanks. I've no experience with Delta robots and I don't know about the servo you posted. Looking at the numbers the resolution is about 0.9 deg. If that is "good enough" must be your decision. Keep the payload as low as possible. Btw, what tasks does your robot have? Pick and place or drawing?

    Would recommend doing some actual testing of the servo first. You might need to calibrate the center and the outer positions. Also check the linearity.

    Good luck!
    Kåre Halvorsen aka Zenta
    ---------------------------------
    Zenta's YouTube channel
    Zenta's Blog
    Zenta's Instagram

  8. Re: Suggest a Microcontroller for Delta Robot Project

    Quote Originally Posted by tician View Post
    given a space-frame and loading (system design requirements), what is the torque experienced/required at the supports (required component minimum specifications).
    I have proposed that at the end effector, robot would be able to pick n place a ping pong ball using suction. I think 16Kg-cm servo will have enough torque for this task (for given the link lengths of 6cm and 26cm of lower and upper arms).

  9. Re: Suggest a Microcontroller for Delta Robot Project

    Quote Originally Posted by tician View Post
    Will you stop with the 'arduino not a solution' crap? Even a long-time obsolete 86HC11 is fully capable of controlling three cheap hobby servos simultaneously. Have you not seen some of the very awesome 3/4-DOF per leg, 4/6-legged crawlers controlled by the SSC-32 (ATmega328)? They require a lot more PWM servos to be accurately controlled in parallel than your delta, yet no issues whatsoever smoothly walking and dancing.
    As I have told you that I am new to servo control using Arduino. There are numerous posts on "How to simultaneuously control multiple servos using Arduino". And responses are: Arduino is not a parallel controller, when it is writing value to a servo using servo library, it gets busy in that tast so it will send pulses to next servo after finishing fisrt servo task. Some guys say that pwm of arduino is limited to be as low as 450 Hz so it is very difficult to drive hobby servo with 20, 30 or 50 Hz frequency. There are some guys who talk about multitasking on arduino using occam-pi or protothreads. Some have made algorithms of nested loops to write two or more servos simultaneously.

    So what I have told in my previos reply about controlling servos using Arduino is based on what I have found on arduino and other forums.

    Selecting a parallel microcontroller like Prallax Propeller will not be a bad choice, I think.

  10. Re: Suggest a Microcontroller for Delta Robot Project

    Quote Originally Posted by Zenta View Post
    Would recommend doing some actual testing of the servo first. You might need to calibrate the center and the outer positions. Also check the linearity.

    Good luck!
    I am currently sorting out the servo and microcontroller selection problem. After sorting it,my next step will be mechanical assembly and electronics of robot. Then I will move to kinematics, dynamics, trajectry and path planning. And then apply the control algorithms for driving the robot.

    Btw thanks for advice!

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Question(s) My Delta Robot
    By Scope in forum Software and Programming
    Replies: 8
    Last Post: 07-31-2013, 02:26 PM
  2. Delta Robot
    By EdrZero in forum Robotics General Discussion
    Replies: 7
    Last Post: 03-14-2013, 04:09 AM
  3. Project Edge avoider robot without microcontroller
    By robotprince in forum Project Showcase
    Replies: 0
    Last Post: 10-31-2012, 11:18 PM
  4. Project Delta Robot for Light Manufacturing
    By Intechmr in forum Projects For Request and/or Sale
    Replies: 1
    Last Post: 10-17-2009, 08:42 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •